The invention generally relates to devices for assisting patients having reduced hearing capabilities and more particularly to an improved ear mold for intensifying the sound produced by a hearing aid, characterized by an electronic amplifier and transducer.
An ear mold, as is readily appreciated by those familiar with such devices, comprising a device made of various types of plastic, both hard and soft, which when inserted into an ear canal and connected to an electronic hearing aid, via a tube or similar conduit, serves to conduct sound energy to the tympanic membrane or ear drum of a patient's ear for thus enhancing hearing capabilities.
It has been found, in practice, that the human ear canal possesses certain resonant characteristics. In free-field tests using an open canal, with 70 DB input, it has been found that from 1,000 hz to 2,800 hz there is a 12-14 DB rise, then a 10 DB drop at higher frequencies of 4,000 to 5,000 hz. Such tests have revealed that when a conventional ear mold is inserted into the ear canal, most of the resonance of the ear canal is lost. Consequently, in such instances, sound energy supplied by a hearing aid, unmodified by resonance, is conducted to the tympanic membrane. Since most hearing aids simply are incapable of greatly amplifying the higher frequencies, because of attendent feedback, the loss of resonance which attends insertion of an ear mold into the ear canal becomes a critical limiting factor in achieving maximum efficiency in the utilization of conventional hearing aids and ear mold combinations.